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lostagain
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Joined: 06 Sep 2016
Location: Quaker Hill, CT
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Topic: Caulking the 'spoiler' Posted: 21 Jul 2020 at 3:21pm |
Looking at the photo reminds me where the tanks were. Black and gray forward, fresh aft. Sorry for the bad memory. It's been almost a year since we sold our 172.
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Never leave footprints behind.
Fred & Maria Kearney
Sonoma 167RB
Our Pod 172
2019 Ford F-150 4x4 2.7 EcoBoost
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offgrid
Senior Member
Joined: 23 Jul 2018
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Posts: 5290
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Posted: 21 Jul 2020 at 2:53pm |
OK, I feel better now, I thought I recalled the 172's having the tanks the other way. I wonder why they changed it?
That's the problem: the intuitive approach doesn't really work.
Once you know the actual tongue weight under one loading condition, the math is pretty easy for any load you add or remove. Like this:
Change in tongue weight is:
added weight X distance from added weight to axle / distance from tongue to axle.
Add to original tongue weight for load in front of the axle, subtract from tongue weight for load added behind the axle. If you remove load subtract when in front of the axle, add for behind.
30 gallons of water is 250 lbs. That's it.
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft
2015 Rpod 179 - sold
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marwayne
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Joined: 25 Oct 2011
Location: Edmonton AB Can
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Posted: 21 Jul 2020 at 2:52pm |
We have a 2011 - 172 grey and black tank in front of axle
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If you want something done right, do it yourself.
2011 RP172, 2016 Tundra 5.7 Litre, Ltd.
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Phil from Maine
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Joined: 12 Jul 2020
Location: 04074
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Posted: 21 Jul 2020 at 2:02pm |
Intuitively, predicated on our discussion here, I would think that having the black and gray forward would do more to balance the TT along the 60-40 ratio than having them in the back.
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lostagain
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Joined: 06 Sep 2016
Location: Quaker Hill, CT
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Posted: 21 Jul 2020 at 1:28pm |
2009
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Never leave footprints behind.
Fred & Maria Kearney
Sonoma 167RB
Our Pod 172
2019 Ford F-150 4x4 2.7 EcoBoost
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Phil from Maine
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Joined: 12 Jul 2020
Location: 04074
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Posts: 19
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Posted: 21 Jul 2020 at 1:16pm |
Originally posted by lostagain
Our 172 had the black and gray tanks aft of the axle and fresh forward. It's something you have to keep in mind when practicing the Zen of trailer balancing. Gallon containers of drinking water help serve as moveable ballast and can be easily refilled if need be. |
Hmmm..........what year R-172?
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lostagain
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Joined: 06 Sep 2016
Location: Quaker Hill, CT
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Posted: 21 Jul 2020 at 12:50pm |
Our 172 had the black and gray tanks aft of the axle and fresh forward. It's something you have to keep in mind when practicing the Zen of trailer balancing. Gallon containers of drinking water help serve as moveable ballast and can be easily refilled if need be.
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Never leave footprints behind.
Fred & Maria Kearney
Sonoma 167RB
Our Pod 172
2019 Ford F-150 4x4 2.7 EcoBoost
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offgrid
Senior Member
Joined: 23 Jul 2018
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Posts: 5290
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Posted: 21 Jul 2020 at 11:11am |
Ok, I stand corrected on the tank locations, hard to keep track of all the different floorplans. I know that on my 179 the tongue weight changes by close to 3% when my 30 gallons of water makes its way from my fresh water tank to my gray tank. So I have my loading set up that I'm at 14% with the fresh tank full and 11% with they gray tank full. I mostly boondock but if you don't and dump before you leave camp you don't have that problem.
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft
2015 Rpod 179 - sold
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Phil from Maine
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Joined: 12 Jul 2020
Location: 04074
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Posts: 19
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Posted: 21 Jul 2020 at 10:55am |
Actually, on the 2011 R-POD both the black and gray tanks are located forward of the axle. The fresh water tank is located aft of the axle. However, I understand the concept you are putting forth.
You obviously know your stuff. Thanks for the education.
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offgrid
Senior Member
Joined: 23 Jul 2018
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Posted: 21 Jul 2020 at 10:32am |
There is no formal specification for safety factor in vehicle frame design. In fact the numbers used by vehicle manufacturers are considered trade secrets. Guidance in the trucking industry is 2.5 to 3x for bump loads. Cars and pickups are higher. Rpods are significantly less than that. There have been numerous instances of axle failures in rPods. So I would assume nothing about the way FR did their design calcs.
That being said, the 172 is probably in the best shape as far as the frame and axle goes as it is a light rPod. The failures have all been in the heavier trailers in the series I believe. OTOH, 172's are one of the ones that has exhibited sway. It will most likely occur when the black and gray tanks are full as they are both behind the axle. Loading additional weight on the rear won't help that. Like I said, you can do what you want but my recommendation remains to verify your actual tongue weight percent under worst case aft loading conditions and be sure you're over the magic 10% number.
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft
2015 Rpod 179 - sold
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